The research program is to continue studies on insulin secretion by the beta cell with a particular emphasis on the initiation of insulin release from the beta cell following glucose stimulation. An in vitro perifusion model has been developed for studies on alloxan inhibition of glucose-induced insulin release from perifused rat islets. Studies are in progress using alloxan as a possible probe for glucoreceptors, on the beta cell membrane. The protective action of anomers of glucose agents affecting cAMP metabolism, epinephrine, cytochalasin B and concanavalin A are in progress as well as studies on the effect of these agents on hexose transport in isolated islets. A modification of the collagenase technique for isolating islets has been developed which increases markedly the yield of islets. This procedure is being used for mass isolation of islets for cell fractionation studies and isolation of plasma membranes. A method for long-term in vitro perifusion of isolated islets is being developed which will be used for studies on zinc metabolism in the islets as well as other studies on inducing beta cell replication and for studies on transplantation of islets. Studies on the extraction of myosin and localization of myosin by fluorescent- antibody techniques in islet cells are in progress. Studies on the role of the microtubular-microfilament system in beta cell secretion and changes in the ratio of microtubulin to microtubules in isolated islets under different experimental conditions will be continued.